Re: [PATCH 00/26] generic btree implementation, version 3

[Christoph Hellwig <hch@lst.de>]

On Mon, Aug 04, 2008 at 11:54:25AM +1000, Dave Chinner wrote:
> > I'm not sure
> > what to do with move_* - these are the most ugly helpers, so maybe
> > we should just make them memmove wrappers in the style of copy_
> > and leave all addressing to the callers.
> 
> Yes, it would be nice to have them use the same interface. If
> we do that, then there's no real point for having a copy vs move
> distinction - we could just make everything use the
> memmove version and drop one of the interfaces altogether....

I've actually come up with another variant.  Since what we do in the
memmove case is to move a number of entries in a single block up or down
one position I've added the following helper:

STATIC void
xfs_btree_shift_keys(
	struct xfs_btree_cur    *cur,
	union xfs_btree_key     *key
	int                     dir,
	int                     numkeys)
{
	char			*dst_key;

	ASSERT(numkeys >= 0);
	ASSERT(dir == 1 || dir == -1);

	dst_key = (char *)key + (dir * cur->bc_ops->key_len);
	memmove(dst_key, key, numkeys * cur->bc_ops->key_len);
}

and the same for ptrs and recs.  This follows the original code in
spirit and is quite readable.